1. Field of the Invention
The invention pertains to the field of concentric camshafts. More particularly, the invention pertains to a concentric cam with check valves in the spool for a cam torque actuated phaser.
2. Description of Related Art
Cam in cam systems are well know in the prior art. In prior art cam in cam systems, the camshaft has two shafts, one positioned inside of the other. The shafts are supported one inside of the other and are rotatable relative to one another for a limited axial distance.
U.S. Pat. Nos. 5,165,303 and 5,577,420 disclose a cam in cam system in which the inner cams are contained on the inner shaft and cam lobes extend through the inner and outer shafts through slots. The outer shaft provides a base circle cam surface for the lobes of the cams connected to the inner shaft.
Unlike in prior art U.S. Pat. No. '303 and U.S. Pat. No. '420, both sets of cams are movable about or fixed to the outer shaft, not the inner shaft, the lobes of the first set of cams do not extend though slots of the second shaft, and the second shaft does not have a means for providing base circle cam surfaces for the lobe portions of the first set of cams.
U.S. Pat. No. 5,664,463 discloses a system in which an outer shaft includes individual longitudinal portions which are connected to one another. The inner cams are connected to the inner shaft by a first form fitting means and the outer cams are connected to the other shaft by a second form fitting means. The inner cams form slots which cover a sector of a circle and are penetrated by axial finger portions of the outer shaft.
The present invention does not have an outer shaft with individual longitudinal portions or axial finger portions, nor do the inner cams form slots.
U.S. Pat. No. 6,725,817 discloses a camshaft assembly that includes an inner shaft surrounded by an outer sleeve or tube which can rotate relative to the inner shaft through a limited angle. One set of cams is directly connected to the outer tube. A second set of cams is freely journalled on the outer tube and is connected to the inner shaft by pins which pass through tangentially elongated slots in the outer tube. The end of the inner shaft projects at the front end of the engine and carries the drive sprocket, which incorporates a variable phase drive sprocket.
The drive mechanism of the variable phase drive sprocket includes a drive member connectable for rotation with the engine crankshaft and two driven members each connectable for rotation with respective sets of the cams. Each of the driven members is connected by a vane-type hydraulic coupling for rotation with the drive member. The hydraulic coupling is such that the angular position of each of the driven members may be varied relative to the drive member, independent of the other drive member. In other words, a cam-in cam system with a dual phaser.
The present invention only has one driven member coupled for rotation with the drive member by means of vane-type hydraulic coupling and one driven member is fixed. The driven members cannot be adjusted independently of one another.
U.S. Pat. No. 6,725,818 discloses a camshaft comprises an inner drive shaft journalled within an outer tube. Cams are directly mounted on the outer tube for rotation therewith and other cams are freely rotatable around the outer tube and connected for rotation to the inner drive shaft by a hollow pin that passes through a hole in the outer tube.
In a first embodiment, the connecting pin is formed with two different diameters, with the central portion of the pin having a diameter less than the diameter of the two ends.
In a second embodiment, a tapered thread or an interference fit thread is provided on an element that is screwed into the bore of the connecting pin to fix the pin in position in the inner drive shaft.
In a third embodiment, one or more spherical elements are pushed into the bore of the connecting pin to expand it into the bore in the inner drive shaft.
In a fourth embodiment, the connecting pin has a mandrel forced through it, which is sized such that the central portion of the connecting pin is expanded beyond its elastic limit and therefore remains an interference fit in the inner drive shaft after the mandrel has been removed.
In the present invention, the connecting pin is dimensioned to be a clearance fit, not a close fit. The pin of the present invention, unlike prior art U.S. Pat. No. '818 has a constant inner diameter, a small diameter region is not present. Plus, the present invention does not insert an element of a larger diameter into the pin to expand the pin.
In U.S. Published Application No. 2005/0279302, a vane-type phaser driven by a crankshaft drives the inner shaft and the outer tube of a first single cam phaser camshaft which is coupled for rotation with the inner shaft and the outer tube of a second single cam phaser camshaft by drive links. The drive links are meshing gearwheels. The phaser may alter both the inner shafts and outer tubes of both camshafts or individual single vane-type phasers may each transmit torque to the first and second camshafts.
The first and second camshafts each have cams formed directly on the two inner shafts and other cams formed on the two outer tubes. Cams that rotate with the outer tubes have collars coupled to the outer tube by heat shrinking and cams that rotate with the inner shaft are loose fit on the outer tube and are connected to the inner shaft by pins that pass through the circumferentially elongated slots in the outer tube.
The present invention does not use drive links to ensure that each group of cam lobes on the first camshaft rotates in unison and drives a second camshaft with a corresponding group of cam lobes on a second camshaft.
U.S. Published Application No. 2006/0185471 discloses a camshaft including an inner shaft and an outer tube surrounding and rotatable relative to the inner shaft. Two groups of cam lobes are mounted on the outer shaft, with one group fast in rotation to the outer tube and the other group rotatably mounted to the outer tube and connected for rotation with the inner shaft by pins that pass with clearance through slots in the outer tube. A sleeve rotatably mounted on the outer tube is connected to impart drive to the inner shaft by a pin passing with clearance through a circumferentially extending slot in the outer tube.
In the present invention, a sleeve is not rotatably mounted on the outer sleeve at all and therefore cannot be connected to the inner shaft to impart drive to the inner shaft.
U.S. Published Application No. 2006/0207538 discloses a camshaft formed of an inner shaft and an outer tube, both of which rotate with respective groups of cams. A drive train driving the inner shaft and outer tube includes a phaser for varying at least one group of cams relative to the phase of the crankshaft. The phaser is secured to the front end of the outer tube and the inner shaft is connected to the front side of the phaser by a driving member.
The phaser in the present invention is not mounted to the front end of the camshaft by a component arranged on the front side of the phaser. The present invention also does not contain a driving member overlying the component axially retaining the phaser on the outer tube and coupling the front side of the phaser for rotation with the inner shaft of the camshaft.
WO 2006/000832 discloses a phaser shifts the phase of the camshaft relative to the engine crankshaft. The phaser may be hydraulically operated or may rely on the reversal of reaction torque of the valve train. The camshaft has an outer tube journalled in bearings in the cylinder head, acting as a phased rotary member and carries of the all of the cams which are phased. The outer tube supports an inner shaft corresponding to an unphased rotary member, serving to transmit torque to an auxiliary device.
In alternative embodiment, the camshaft includes a journalled outer tube supporting an inner shaft. Only some of the cams are mounted on the outer tube and rotate with it. The remaining cams rotate about the outer tube and are coupled for rotation with the inner shaft by pins that pass through tangentially elongated slots in the outer tube. To avoid the pins passing through the cam lobes, each of the cams that rotate with the inner shaft is formed with an annular extension which receives the pin.
In both embodiments, the phaser is used to drive the phased member or outer tube of the camshaft.
In the present invention, an auxiliary device is not connected to be driven by torque transmitted from the crankshaft through the first rotary member of the camshaft or the inner shaft and is not even present at all.
WO 2006/067519 discloses a phaser with a drive member and a driven member. The drive member comprises a disc with at least one arcuate cavity that is open at both axial ends. The driven member comprises two closure plates sealing off the arcuate cavities at the axial ends and at least one vane formed separately from the closure plates. The vane is moveably received within the cavity and divides the cavity into two chambers. Each vane is secured at both its axial ends by the closure plates.
The phaser is fitted to a camshaft assembly comprised of an inner shaft and an outer shaft. The outer shaft has a threaded end engageable with an internal screw thread formed in the disc. The inner shaft has an internal thread that is engaged by the thread of a bolt that passes through an axial pre in the closure plate and acts to clamp the closure plate against the axial end of the inner shaft. The outer shaft rotates with the driven member or the disc and the inner shaft rotates with the drive member or the closure plates. Different groups of cams are fast in o rotation with each of the shafts. The phaser will alter the phase of some of the cams relative to the crankshaft, while other cams are always rotated in the same phase relative to the crankshaft.
In the present invention, the vanes are not secured at both axial ends to two closure plates or ends plates, they are formed integrally with the rotor, as is conventional with vane phasers.
WO 2006/97767 discloses a camshaft assembly comprised of an inner shaft and an outer tube surrounding and rotatable relative to the inner shaft. Two groups of cam lobes are mounted on the outer shaft, with one group fast in rotation to the outer tube and the other group rotatably mounted to the outer tube and connected for rotation with the inner shaft. The connection between the cam lobes and the inner shaft is effected by driving members whose positions are adjustable in order to compensate for significant manufacturing inaccuracies between the inner shaft and its associated group of cam lobes.
In the present invention, the driving members connecting the inner shaft to the cams are not adjustably to compensate for significant manufacturing inaccuracies between the inner shaft and its associated group of cam lobes.
U.S. Published Application No. 2006/0207529 discloses a camshaft assembly including an inner shaft and an outer tube surrounding and rotatable relative to the inner shaft. Two groups of cam lobes are mounted on the outer shaft, with one group fast in rotation to the outer tube and the other group rotatably mounted to the outer tube and connected for rotation with the inner shaft by pins that pass with clearance through slots in the outer tube. A spring is incorporated into the camshaft assembly to bias the inner shaft relative to the outer tube towards one extreme of its angular range. A phaser is mounted to the camshaft assembly by a conventional flange and bolt arrangement.
In the present invention, the inner tube of the camshaft assembly runs entirely through the phaser, to act as a sleeve for the spool control valve, and the outer tube fastens to an extension of the sprocket. The present invention does not attach the phaser to the camshaft assembly using a conventional flange and bolt arrangement.
DE 39 43 426 discloses a camshaft with two shaft elements one inside of the other, either of which can be moved with respect to each other. First cam elements are connected to the inner shaft and second cam elements are connected to the outer shaft. The outer shaft has apertures which received pins that connect the first cam elements with the inner shaft. The cams are fastened by pins on both sides of the cam, not just on one side (i.e. through one hole).
In the present invention, the pins do pass entirely through the inner shaft and the slots in the outer tube, through two slots penetrating the outer tube.